Measuring Nanoscale Torques with Cylindrical-Polarization-based Interferometric Scattering Microscopy
Authors:
Milan Vala,
Ivan Kopal,
Lauren Takiguchi,
Yevhenii Shaidiuk,
Vítězslav Lužný,
Łukasz Bujak,
Pallav Kosuri,
Marek Piliarik
Abstract:
The ability to observe rotational dynamics and measure underlying torques is a crucial component in understanding the function and mechanics of nanoscale systems. Yet, direct observation of rotational dynamics at the single-molecule level in liquids remains challenging due to the trade-off between optical detectability and hydrodynamic responsiveness. Labels that are bright enough for rapid readou…
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The ability to observe rotational dynamics and measure underlying torques is a crucial component in understanding the function and mechanics of nanoscale systems. Yet, direct observation of rotational dynamics at the single-molecule level in liquids remains challenging due to the trade-off between optical detectability and hydrodynamic responsiveness. Labels that are bright enough for rapid readout typically introduce excessive drag, while minimally perturbing probes are difficult to detect at high speed. This limits access to fast rotational dynamics required for direct torque measurements. Here, we introduce cylindrical-polarization-based interferometric scattering microscopy (cypiSCAT), a method encoding the orientation of anisotropic scatterers directly into a single interferometric point spread function, while intrinsically suppressing the isotropic background. We achieve rotational tracking of low-drag orientation labels based on DNA origami-attached gold nanorods with sub-degree angular precision and microsecond temporal resolution, allowing quantitative characterization of nanoscale rotational dynamics. This capability provides direct access to torque metrology at the single-molecule level, here demonstrated through the extraction of optically induced torques as small as ~1 pN nm. Relying on elastic scattering, cypiSCAT combines ultrafast temporal resolution with long observation times, making it well-suited for capturing rapid and rare rotational events and reaction steps in nanoscale biomolecular systems.
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Submitted 15 June, 2026; v1 submitted 13 January, 2026;
originally announced January 2026.
Photothermal Fourier-plane Phase Synchronization for Interferometric Scattering Microscopy
Authors:
Shupei Lin,
Nanfang Jiao,
Yevhenii Shaidiuk,
Delong Feng,
Jingwei Luo,
Yihao Yu,
Lukasz Bujak,
Jianwei Tang,
Marek Piliarik,
Xue-Wen Chen
Abstract:
We introduce and experimentally implement Fourier-plane phase synchronization for optical microscopy, and demonstrate its performance with interferometric scattering microscopy. By combining a photothermal phase plate and laser beam scanning, we realize a synchronized phase for all scattering components on the Fourier plane of high numerical-aperture microscopes, where the evanescent waves and opt…
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We introduce and experimentally implement Fourier-plane phase synchronization for optical microscopy, and demonstrate its performance with interferometric scattering microscopy. By combining a photothermal phase plate and laser beam scanning, we realize a synchronized phase for all scattering components on the Fourier plane of high numerical-aperture microscopes, where the evanescent waves and optical aberration normally produce highly inhomogeneous phase distributions. We achieve an almost perfect point spread function, exhibiting a tighter focus with 50\% enhancement of the signal and ideal circular symmetry. Particularly, by synchronizing the phase to $π/2$, we demonstrate the background speckles exhibit an anti-symmetric dependence on axial defocus, enabling the effective suppression of the speckles via defocus integration and thus the detection of 10 nm particles immobilized on the substrate. The concept and technique of seamless dynamic phase control on the Fourier plane constitute a key asset for modern optical microscopy.
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Submitted 8 November, 2025; v1 submitted 17 October, 2025;
originally announced October 2025.